As the dimensions of transistor devices continue to shrink and the packing density improves, more complex integrated circuits are being produced in which different portions of the circuit may exhibit different behaviors over the life of the device. As a result, electrical fuses or e-fuses are being used in semiconductor devices to adapt the performance of certain circuit portions to comply with the performance of other circuit portions. E-fuses represent electronic switches that may be activated once to provide a desired circuit adaptation; once programmed the programmed state of an electrical fuse is irreversible. For this reason, electrical fuses are referred to as one-time-programmable (OTP) elements.
Programming or lack thereof constitutes one bit of stored information associated with an electrical fuse. Semiconductor fuses have a relatively low initial resistive state that may be changed to a relatively higher resistive state through programming, e.g., through electrical bias conditions applied to the fuse. Conventionally, fuses have been formed from the semiconductor material, such as polysilicon, concurrently with the semiconductor gate electrodes. However, as transistors have decreased in size, the polysilicon gate electrodes have been replaced with metal electrodes which are formed by gate last technologies, such as replacement gate processes. With the polysilicon removed, polysilicon fuses can no longer be built. Back-end-of-line (BEOL) metal fuses have, therefore, been implemented instead of the polysilicon fuses. However, standard metal fuses formed BEOL require a high programming current and occupy a significant amount of space, as they entail multiple metal layers and vias and include bent metal portions.
A need therefore exists for methodology enabling formation of fuse structures that may be programmed at relatively low power supply voltages and occupy less semiconductor real estate, and the resulting devices.